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        // function fn(data) {
        //     let a = data.a;
        //     let b = data.b;
        //     let c = data.c;

        //     if(c === undefined) {
        //         c = 100;
        //     }
        // }
        // fn({a:10,b:20});


        // function fn(data) {
        //     let {x:a,y:b,z:c=100} = data;
        //     // let {a,b,c=100} = data;
        //     console.log(a,b,c);
        // }
        // fn({x:10,y:20});


        // let [a,b,c=90] = [7,8];
        // console.log(a,b,c);



        // function f() {
        //     console.log("xx");
        // }
        // let [x=f()] = [];


        // let [a,b=a] = [1];
        // console.log(a,b);


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